Yoshitoshi Watanabe

Novel SPICE model for common mode choke including complex permeability

A highly accurate filter simulation requires a high precision SPICE model for the common mode choke. Conventional SPICE models for chokes consist of parallel RLC circuits and show a substantial difference between the measured and simulated impedance characteristics due to the lack of frequency-dependent complex permeability considerations. Here, we propose a novel SPICE model for a common mode choke that includes the frequency-dependent complex permeability. This model uses a transfer function in the s-domain to describe frequency-dependent elements. Moreover, two model parameter estimation methods are proposed; a measurement based method and a datasheet based method. High accuracy is achieved with the measurement based model by extracting the model parameter using the measured impedance characteristics of the actual coil. In the datasheet based method, the model parameter is estimated from the datasheet and the shape of the coil without the actual coil. Finally, we show that not only the impedance characteristics of a choke can be expressed, but also the insertion loss of a T-type filter can be predicted much more accurately than presently possible using a conventional model. This SPICE model is the first to express the frequency-dependent inductance and resistance of the choke with high accuracy; therefore, it is expected to be useful for filter design.